Add vars file for debian buster

Depends-On: https://review.opendev.org/711112
Change-Id: I291c0d76029639c40050e3271d1dce1cb4c8d65e

vars/debian-10.yml

@@ -0,0 +1,19 @@
+---
+# Copyright 2018, Rackspace US, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+_nspawn_map:
+  distro: debian
+  arch: "{{ nspawn_architecture_mapping[container_architecture] }}"
+  release: buster